# ACD/Labs Blog

## Logic Puzzle #43: Is Signal Intensity on a Mass Spectrum Problematic? … Solution

The warning flag for this puzzle is evident in the intensities of the signals. For an unknown compound, the TOF-ESI+ mass spectrum below shows the expanded region around four isotope clusters at m/z 300.336 ([M+H]+), 322.307 ([M+Na]+), 599.672 ([2M+H]+) and 621.611 ([2M+Na]+). The intensities of the 13C isotopes (i.e. the [M+1] signal) vary between 40...

## Logic Puzzle #43: Is Signal Intensity on a Mass Spectrum Problematic?

A key element in data interpretation is to identify any warning flags. Warning flags can help a chemist differentiate good data from bad data. For an unknown compound, the TOF-ESI+ mass spectrum below shows the expanded region around four isotope clusters at m/z 300.336 ([M+H]+), 322.307 ([M+Na]+), 599.672 ([2M+H]+) and 621.611 ([2M+Na]+). Are the intensities...

## Logic Puzzle #42: How to Convert to PPM for NMR and MS Data? … Solution

Many analytical data rely on common calculations. This solution shows the formula used in the calculations. NMR and MS data were collected on two unknown compounds. The TOF-MS data shows the [M+H]+ at m/z 300.0000 and 600.000 at an error of 0.001 Da. The 500 MHz 1H NMR spectrum shows two chemical shifts at 1500.00...

## Logic Puzzle #42: How to Convert to PPM for NMR and MS Data?

Many analytical data rely on common calculations. This puzzle covers one such common calculation. NMR and MS data were collected on two unknown compounds. The TOF-MS data shows the [M+H]+ at m/z 300.0000 and 600.000 at an error of 0.001 Da. The 500 MHz 1H NMR spectrum shows two chemical shifts at 1500.00 and 3000.00...

## Logic Puzzle #41: Using MS TOF data to Determine the Molecular Formula … Solution

Working on poorly collected data is not fun. It can be frustrating and time consuming. A good LC-MS+ TOF dataset is consistent across a peak and exhibits a mass measurement accuracy of < 5 ppm. The TOF data below shows a significant variation across the peak m/z 205.136 to 205.076 to 205.096 (range m/z 205.106...

## Logic Puzzle #31: Are the Signals Related? … Solution

To identify co-eluting components on a chromatogram, one searches for any distinct differences between the components. There are basically three criteria to check the XICs (extracted ion chromatograms) for to confirm whether the m/z signals pertain to the same component: line shape, signal apex and retention time range. The XICs for m/z 188.1 and 205.1...

## Logic Puzzle #31: Are the Signals Related?

Sorting out what compounds are present in a mixture is a difficult task. The process is further complicated when the compounds co-elute on a chromatographic run. An LC/MS (ESI+) was collected for an unknown sample comprising of small organic molecules. The total ion chromatogram (TIC shown in black) shows a signal at 2.86 minutes. The...

## Logic Puzzle #24: Conflicting Masses? … Solution

The explanation offered herein covers one possible scenario to a complicated situation. Please note that other explanations are possible. The LC/MS data shows an unknown at 1.8 minutes exhibiting an [M+H]+ at m/z 260 and an [M-H]- at m/z 256. The difference of 4 mass units lends itself into a scenario of conflicting data. One...

## Logic Puzzle #24: Conflicting Masses?

The purpose of this puzzle is to examine data collected from multiple detectors with the hopes of sorting out the conflicting data surrounding the unknown. In an attempt to identify the structure for an unknown, UPLC data was collected using a C18 column with a run time of 2.2 minutes. The UV, ESI- and ESI+...

## Logic Puzzle #22: The Art of Uncovering the Molecular Formula

It is fairly route for an elucidator investigating an unknown compound to relate data from multiple spectroscopies. This puzzle aims at establishing a molecular formula from a set of spectroscopic data. For an unknown organic, a ESI(neg.)-ToF mass spectrum for a singly-charged species and a 13C NMR spectrum are supplied below. In addition, the 1H...